A dry well is a stormwater runoff reduction tools that can be used to achieve the goals of minimizing hydrologic changes associated with urbanization. As impervious surfaces expand with urbanization, rain is unable to penetrate the soil. This creates large volumes of runoff that are typically directed into piped stormwater conveyance system which increases the volume of runoff and the speed in which it reaches local waterways. This change in the urban hydrograph reduces the potential for groundwater recharge and damages aquatic habitat in creeks and rivers. Dry wells can help minimize these effects by allowing stormwater to bypass soils with poor infiltration rates (Class C and D soils) to reach more permeable layers.
These qualities of dry wells make them a useful tool to help meet stormwater management requirements issued by the State and Regional Water Boards throughout California. Dry wells also provide a sustainable and environmentally friendly drainage solution that avoids costly, underground mechanical devices and can serve as a Low Impact Development (LID) tool. Dry wells can incorporate pretreatment features such as grassy swales and sedimentation basins for additional stormwater treatment. Dry wells can protect waterways from erosion caused by direct stormwater discharge and reduce the harmful effects that traditional stormwater management practices have had on the aquatic ecosystem. Dry wells not only aid in stormwater runoff reduction and increase groundwater recharge, but they can also minimize the risk of flooding, are economical and have minimal space requirements.